Stepladder



Jan. 13, 1959 H. T. GROVES STEPLADDER Filed June 16, 1954 INVENTORHOWARD T. Graovzs ATTORNEYS STEPLADDER Howard T. Groves, Parsons, Kane.

Application June 16, 1954, fierial No. 437,035

1 Claim. ((Il. 228-411) This invention relates to step ladders andparticularly to V-type or straddle type ladders.

As is well known in the art, straddle type ladders comprise two basicstructural members, namely a stile having a desired number of steps anda backbrace or prop for supporting the stile. These two members areusually hingedly connected at the top to form an inverted V when thefeet of the ladder are spread in erecting the ladder. Conventionally,means are provided to limit the spread between the stile and backbrace.

Because ladders of this type have four point support, there being twofeet each on the stile and the backbrace, it is essential tothe'stability and safety of known forms of these ladders that they beerected on a perfectly level surface. Even small irregularities,particularly on a hard surface, result in one leg of the ladder failingto make contact so that the ladder tends to wobble when the user shiftshis weight, "which can cause him to lose his balance and fall from orcapsize the ladder. In addition to the dangerous lack of stability whichresults when such ladders are set up on an uneven surface, a severewrench or twisting stress is imposed on the ladder structure when aweight is placed on it, which stress eventually so loosens the steps orrungs, the brace members and joints that the ladder becomes too wobblyand insecure for use even on perfectly smooth and level surfaces.

Efforts have been made in the past to eliminate these difficulties asshown, for example, by the patents to Call, Patent No. 2,397,468 and toRuse, Patent No. 1,928,158. These efforts, however, have been at bestonly partially successful.

For example, ladders of the type shown by Gail are limited to a fixednumber of relative lateral angular positions between stile and backbraceand therefore unless one of these positions conveniently suits theparticular irregularities encountered on the support surface, the ladder will not be steady. Furthermore, in any position of adjustment ofthe ladder, the stile and backbrace are so connected that thedeleterious efiects of twisting stresses on the structure are noteliminated.

The ladder disclosed by Ruse provides for adjustment of the feet of thestile without definite limiting positions but the manner in whichadjustment is accomplished makes it necessary that both of the legs ofthe backbrace be independently adjustable in length. The result is arelatively complex and unwieldy structure requiring trial and errorlevelling involving manual adjustment of the length of either or bothlegs of the backbrace.

The present invention in its broadest aspects contemplates a straddletype ladder in which the foregoing disadvantages of prior art laddersare completely eliminated by means of a ladder structure wherein thebackbrace and stile are adapted for relative pivotal movement about anaxis normal to the plane of the bacltbrace.

It is a further general object of the present invention to provideimproved straddle type step ladders adapted to provide stable support onuneven surface.

it is another object of the invention to provide a novel straddle-typestep ladder which automatically adjusts itself to irregularities smallor large in the surface on which it is supported thus invariably andinherently assuming a stable, steady position when erected.

Still another object is the provision of an improved straddle type stepladder characterized by the absence of wrenching or twisting stresses inits structure regardless of the irregularity of the surfaces on which itis erected and mounted.

A further object of the invention is the provision of an improvedstraddle type step ladder in which the supporting force provided by thebackbrace for the stile is transmitted through laterally extendedcontacting surfaces.

A. still further object of the invention is the provision of an improvedstraddle-type step ladder as characterized by the preceding objectswhich is simple, durable, and inexpensive to manufacture.

These and other objects as well as the many important advantages of thepresent invention will be apparent to those skilled in the art from thefollowingdescription and subjoined claim to be read in conjunction withthe annexed drawings, in which:

Figure l is a perspective elevation of a straddle-type ladder embodyingthe present invention;

Figure 2 is a rear elevation of the ladder shown in Figure l; and

Figure 3 is a fragmental sectional view on line 3-3 of Figure 2, showingdetails of the toggle brace connection between the stile and backbrace.

Referring now to the drawings in which like parts are identified by likereference numerals throughout the several views, 10 indicates, in itsentirety, a straddle-type step ladder embodying the present invention.

Ladder 10 comprises two primary structural components: a stile l2 and abackbrace or prop l4. Stile 12 is made up of a pair of side rails 16which are secured together by a number of transversely extending stepsor rungs 18a, ltib, 18c, and Mid. Side rails 16 are preferably disposedin downwardly diverging relation so as to provide a relative broad baseand therefore, steps ltia liid are progressively shorter in length. Theyare secured to the side rails in any suitable manner, for example, inthe disclosed embodiment the ends of the steps are disposed in shallowgrooves provided on the inner surfaces of the side rails. Transverse tierods 26 running under each step and through the side rails, tie theladder together. Nut and washer assemblies 22 on at least one end of tierods 20 allow the tie rods to be tightened to suflicient tension toeliminate any play or looseness in the parts of stile 12. It will beunderstood that if only one end of the tie rods 2t] is provided with anut and washer assembly, the opposite end has a suitable head orenlargement to prevent its being pulled through the respective siderail.

As clearly shown in Figure 1, a spreader block 24- is provided betweenthe underside of each step 18a-l8d and corresponding tie rod 24 Spreaderblocks 24 are located substantially midway between the ends of the stepsand contain a suitable groove 26 for the reception of the tie rods.. Byvirtue of this construction, a substantial part of the weight placed onthe steps is transmitted through blocks 24 to the tie rods 24 causingthem to flex downwardly and pull the respective side rails together.This action not only reduces flexing of the steps but allows a largepart of the weight placed on steps to be absorbed as compressive forceson the ends of the steps instead of as bending or flexing moments.

The structure of the stile 12 is further reinforced by means of cornerbraces 23 between the ends of the lowermost step 18a and the respectiveside rails 16.

A top step or platform 3d of. the ladder is secured to the upper ends ofside rails 16 by a pair of brackets 32, bolted, riveted or otherwisesecurely fastened to the rails and'p'latform. Brackets 32 serve tohingedly connect the stile l2 and backbrace Mas willhereinaft'er beexplained.

Backbrace 1.4- consists of? apair' of legs '34 secured to- 'gether indownwardly diverg ent' relation by anycoir venient number of crossbraceiiasseinblies 36 and'36r1, preferably in the following manner. Eachbraceassembly 36 and 36a consists of a brace member 38 extendingsubstantially horizontally between legs 34- and having grooves 46 in itsupper and lower longitudinal edges. Brace members are retained and'th'eoppo'sing, legs 34 tied together by a pair ofparallel, horizontaltie rods .42 disposed in the upper and. lower grooves respectively ofthe brace members. The ends of tie rods 42pass through suitable holes inlegs 34 and at least one end of each is threaded and provided with a nutand washer assembly 44 for tightening up the rods. It: willbeunderstood, of course, that if the nut and washer assemblies areprovided at one end of the tie rods only, the opposite end is providedwith a head or othersuitable enlargement to prevent its being pulledthrough the respective leg,

As clearly shown in Figure l, the upper ends of legs 34 are bifurcatedas at 46 to receive and support a quadrant block 48 secured therein bysuitable fasteners t).

Quadrant block 4% consists of a flat plate of wood or other suitablematerial and may be of one piece or multiple piece construction, thelatter type being illustrated. The upper edge 52 of quadrant block 43extends upwardly out of bifurcations 46 and is curved in a relativelylong radius circular are having its center located somewhat below thelower portion of the quadrant block and midway between legs 34.

The lower edge of quadrant block 48 is provided with a relatively deepnotch 53 midway between legs 34. The arcuate edge 52 of quadrant block48 preferably is covered with a strip 54 of high friction wear resistingmaterial secured thereto in any suitable manner for a purposehereinafter appearing. I

Brackets 32 are formed with cars 56 containing Icoaxially aligned holesreceiving and freely rotatably supporting the opposite ends of ahorizontal hinge rod 58 (see Figure 3) eitending therebetween. Hinge rod58 is retained against axial displacement from ears 56 by cotter keys6%) or other convenient means.

A sheet metal yoke 62 having a pair of parallel generally V-shapeddependent legs 64 straddles hinge rod .58.. A crest block 66, having astraight upper edge is block 48 and overlie notch 53. I A nut and boltassembly .76 or equivalent fastening means extends between and connectsthe lower ends of legs 64, approximate center of notch 53. I

From the structure described it will be und rstood that quadrant block48 is retained between the legs 64 of yoke 62 by the cooperation of boltassembly '70 and notch 53 with sufficient play so that the quadrantblock can move laterally, or toward and away from crest block 66 and canpivot about the center of curvature of arcuate passing through the edge52. Thus it will be seen that bolt assembly 76 has free play in notch.53 and therefore, the bolt and notch serve only to maintain the assemblyof the backbrace with the remainder of the ladder when the ladder isbeing carried or erected. j

To limit the spread or separation between stile 16 and backbrace 14, atoggle brace 72 is provided which '4 consists of a pair of links 75% and76, pivotally connected as at 78. The opposite ends of brace 72 areconnected to the rear edge'of step 180 and to cross brace 36a in such amanner as to allow relative pendulous or lateral angular movement of thestile and backbrace. For example, in the disclosed embodiment a nut andbolt assembly 86 extends vertically through step 18c. An ogee-shapedlink 82 has one end looped around bolt 80 and its other end hookedthrough an aperture 84 in brace link 74. The'other end of toggle brace72 is connected to brace member 36a by means of a swivel hook 86 havingits bight portion hooked through an aperture 88 inbrace link 76 and itsstem or shaft'extended through a suitable aperture in brace member 36aand secured by means of a nut 90.

From the foregoing description, it will be understood that thefunctioning of the invention is as follows':' The ladder folds and iserected in the conventional manner and when erected, if the supportingsurface is perfectly level, assumes the solid line position shown inFigure 2.

In the event that the supporting surface is not level the stile 21 andbackbrace 14 are free to pivot angularly with respect to each about thecenter of curvature of arcuate surface 52, the coacting surfaces 52 and69 sliding on each other until the ladder components 12 and 14spontaneously assume a position in which all four feet are firmlyimplanted on the supporting surface. In Figure 2 the backbrace 14 isshown in'phantom lines representing one of an almost infinite number ofrelative positions which can exist between the stile 16 and thebackbrace. An extreme case is shown in Figure 1 wherein a block is usedto represent a high spot on the supporting surface. While in mostinstances, the ladder would not have to compensate for such a greatdifference in height (block 92 is about four inches high in the scale ofthe drawing) it is fully capable of doing so, the ladder as shown inFigure 1 being entirely stable and susceptible of being mounted withcomplete safety. The action of the ladder in compensating for an unlevelsupporting surface is the same regardless of which of the four feetencounter high or low spots.

It is important to note that, when the ladder is mounted, the load istransmitted from the stile to the backbrace by and is substantiallyequally distributed over the contacting arcuate surfaces 52 and 69. Avertical projection of the center of mass of the ladder falls within thecentral portion of the base rectangle having the feet of the ladder asits corners, regardless of the relative angular positions of the stileand backbrace.

The friction strip 54 prevents accidental slippage between the quadrantblock 48 and crest block 66 when a weight is placed on the ladder andtherefore, it'will be appreciated that this strip may be located onthearcuate surface of either the crest block or quadrant block.

The invention may be embodied in other'specific forms without departingfrom the spirit or'essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claim rather than by the foregoing description, and all changeswhich come within the meaning and range of equivalency of the claim aretherefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

A straddle type step ladder comprising a stile including a pair of siderails rigid with respect to each other and a number of steps extendingtransversely therebetween, a backbrace having a pair of spaced legs.rigid with respect to each other and at least one cross brace extendingbetween said legs, a transverse hinge rod securedto saids'tile adjacentthe upper end thereof, a yokeswingabl'y straddling said hingerod andhaving a pair of "spaced parallel planardepending legs, a fiatcrest'bloc'k --rigidlysecured to said yoke between the upper portions ofthe depending legs thereof, a flat quadrant block on the upper end ofsaid backbrace slidably disposed between the lower portions of thedepending legs of said yoke, complementary arcuate surfaces on the upperedge of said quadrant block and lower edge of said crest block,respectively, said surfaces being in the form of relatively long radiuscircular arcs having a common center in the plane of said quadrant blockand crest block and in the vertical plane of symmetry of said ladder,said yoke legs acting as aguide for said quadrant block, and a pin andslot connection between said quadrant block and the legs of said yokeallowing relative rotational and translational movement of said quadrantblock and crest block whereby said arcuate surfaces are in abutment atleast when the ladder is erected, said surfaces carrying the loadtransmitted between said stile and backbrace and allowingsaid stile andbackbrace to assume relative angular positions about said common centerto compensate for irregularities in the surface upon which the ladder iserected.

, References Cited the file of this patent UNITED STATES PATENTS StaringMar. 8, McCormick Oct. 6, McKinney Sept. 6, Franklin Feb. 17, OsterhoudtFeb. 24, Mitchell Apr. 6, Patterson Aug. 8, Blosser Aug. 23, TrowbridgeFeb. 14, Thrasher Jan. 9, Gail Apr. 2, Fowler Oct. 15, Young Mar. 14,Pierce May 26,

